Impulse current repeater



NOV. 10, 1931. c, AHLBERG 1,831,730

IMPULSE CURRENT REPEATER Filed May 10. 1929 Patented Nov. 10, 1931 UNITED STATES PATENT OFFICE OURT FREDRIK AH'LBERG, OF STOCKHOLM, SWEDEN, ASSIGNOR T0 TELEF ON AKTIE- BOLAGET L. M. ERICSSON, 0F STOCKHOLM, SWEDEN, A COMPANY OF SWEDEN IMPULSE connnnzr REPEATER Application filed Kay 10, 1929, Serial No. 362,048, and in Sweden May 12, 1928.

In automatic telephone systems in which the selectors are set by means of current impulses it is necessary that the ratio between the breaking and the closing periods when sending current impulses has a certain value adjusted so as to suit the design and the operation of the selectors which value may be different in different systems. In such plants in which different systems are intended to co-operate with each other it may thus occur that those impulses which are sent by means of impulse senders in one system may not work satisfactorily when extending the con- In the device according to Figure 1, F

designates an impulse sender, by way of example a finger disk by means of which current im ulses maybe sent over a primary circuit BS for instance the subscribers line 7 containing a primary impulse relay A. The

latter relay controls an operating circuit of a secondary impulse relay B and also a holding circuit for an auxillary'relay C which in turn controls the circuit of a slow-acting relay D. The relay B controls together with the relay D a secondary impulse circuit SS. The impulse relay B is according to the invention adapted to attract its armature rapidly when actuated by a current impulse of very short duration and thereupon, to hold its armature energized during a period of time which is constant and may be arbitrarily chosen. Said period may for instance be adjusted by a suitable dimensioning of an ohmic resistance R connected in parallel with the relay coil B. Said period of time is ad- 'usted in respect of those selectors which ave to be controlled over the circuit SS in order to give a certain required length to the breaking periods in the latter circuit. The relay G is a quick-acting relay, whereas the relay D is a slow-acting relay which rapidly attracts its armature but only slowly releases the same. It is adjusted so as to retain its armature energized during the sending of the impulses.

The arrangement functions in the following manner. WVhen the primary circuit 1s closed the relay B receives a current impulse over the contact 1 on the relay A and. the contact 2 on the relay OJ The relay B,asa consequence, attracts its armature and connects itself into a current path independent. .of the former circuit over its contact 3 and the contact 4 of the relay C. At the same time it closes an operating circuit for the relay C at the contact 5 which relay then connects itself into a holding circuit over the contact 6 and at the same time opens the two current paths of the relay B, viz. at the contact 2 and also at the contact 4:. The relay B then de-energizes and'releases its armature after a definite period of time. Almost simultaneously the relay D operates said relay having been connected into circuit over the contact'7 of the relay 0. For this reason the secondary circuit SS at the contacts Sand 9 C, which is thus de-energized. This fact has,

' however, no influence upon the relays B and D, and, as a consequence, the secondary circuit- SS remains closed. When the primary .circuit is again closed, the relay B receives as before a current impulse over the contact 1, the above described switching operation be- 'ing then repeated. The relay B then opens the secondary circuit at the contact 8. The interruption in the latter circuit will be of the same len th of time as the period of time during whici the relay B is energized. As the relay B is quick to operate a current closing of an exceedingly short duration at the contact 1 is suflicient to enable the switching operating and holding windings AL and HL respectively, the holding circuit beingthen arrangement to operate in the described mang dependent on the contact 3 of the relay B ner. A current closing of very long duration at the contact 1 has no disturbing influence on the switching operation as the relay C during this period is in operation and the relay B, as a consequence, is entirely disconnected. It is thus evident that the interruptions in the secondary circuit as regards the required lengths of time are entirely independent of the ratio between the closing and breaking periods in the primary circuit as well as of the absolute value of said periods of time.

Thecondition for attaining such a constant operation of the relay B is that the relay is supplied with a suiiicient excitation energy. In order to assure this condition said special current path over the contacts 3, L is provided. It has namely to be noted that the relay B is energized already before the magnetic field has reached its full force. If now the current closing in the contact 1 should be of an insufficient length of time to enable the relay B to be fully energized by the current passing over said contact, the relay obtains an additional exciting current over the contacts 3 and t which current is sufiicient to enable the held to reach the required force. he supply of exciting current over the contacts3, a takes place during the period of time between the energization of the relays B and O which period is adequate for the purpose in question.

The contacts 3 and on the relay B should be so designed that the contact 3 is closed earlier than the contact 5. If this should not be the case but for instance the contact 5 be closed before the contact 3 the relay G should be able to attract its armature and would break the contact 4 too early, in which case the relay B will not obtain suflicient excitation energy.

Said arrangement of the contacts 3, 5 in such a manner that the contact 3 is closed earlier than the contact 5, on the other hand, results in that the contact 5 is opened earlier than the contact 3 when the relay B is de-energized. If the current closing at the contact 1 should be of such a short duration that the relay G loses its holding current over the contact 1 before B begins de-energizing it may happen that the relay C releases its armature and closes the contact tbefore the contact 3 is opened, the relay B being then anew able to obtain current over the contacts 3, 4 and the relay C again connected into circuit over the contact 5, whereupon the same operation should be repeated so as to start vibration of the relays B and C.

Said inconvenience which may be elimi nated by a suitable adjustment of the relay contact is entirely avoided in the embodiments shown in Figures 1 and 2. For this purpose the relay C is provided with special which contact just as well as in Figure 1 should be so designed as to be closed earlier than the contact 5. The arrangement according to Figure 2 differs also from Figure 1 therein that the circuit of the relay B extends over a normally closed contact '10 of the relay G which contact corresponds to the contacts 2 and 4 in Figure 1. If now the contact 5, as mentioned, upon de-energization of the relay B is interrupted earlier than the contact 3, whereas at the'same time the contact 1 is opened, the de-energization of the relay G can not occur in any-case before the relay B de-energizes, because the relay G in this case obtains holding current over the contact 3 which is not opened before the relay B is de-energized. Any vibration of the armatures of the relays B and G can, as a consequence, not occur.

Figure 3 shows the current operations in the primary circuit PS and the secondary cir cuit SS which is represented by the curves E and G respectively The curve H represents the corresponding movements of the armature of the relay B. The curves are arranged in relation to each other in such a manner that the portions of the curves lying vertically above each other correspond to'the same instant of time.

1 claim 1. In an impulse current repeater, the combination of a primary circuit, a secondary circuit, an impulse repeating relay controlled from the primary circuit and controlling said secondary circuit,an intermediate circuit for the energization of the impulse repeating relay by means of current impulses controlled from the primary circuit, means at the repeating relay to break the secondary circuit upon energization of said relay, an auxiliary relay which upon being energized connects itself into a holding circuit controlled from the primary circuit and means whereby the repeating relay upon being energized connects itself into a holding circuit independent of the primary circuit, the holding circuit of the repeating relay containing a break contact of the auxiliary relay.

2. In an impulse current repeater, thecombination of a primary circuit, a secondary circuit, an impulse repeating relay controlled from the primary circuit and controlling said secondary circuit, an intermediate circuit for the energization of the impulse repeating relay by means of current impulses controlled from the primary circuit, means at the repeating relay to break the secondary circuit upon energization of said relay, an auxiliary relay which upon being energized connects itself into a holding circuit controlled from the primary circuit, means whereby the repeating relay upon being energized connects itself into a holding circuit independent of the primary circuit, the holding circuit of the repeating relay containing a break contact of the auxiliary relay and means Whereby the holding circuit of the auxiliary relay is controlled by the repeating relay in such a manner that it may be interrupted by the latter relay When this is de-energized.

In testimony whereof I aflix my signature.

CURT FREDRIK AHLBERG. 

